1. Technical Field
The invention relates to wheel end assemblies, and in particular to wheel end assemblies for heavy-duty vehicles, such as tractor-trailers. More particularly, the invention relates to an outboard sealing system for a heavy-duty vehicle wheel end assembly. Still more particularly, the invention is directed to a sealing system that includes a seal which cooperates with an axle spindle nut and a hub of the wheel end assembly. The seal is disposed between an outboard bearing and a hubcap of the wheel end assembly, and is formed with features that extend radially between the axle spindle nut and a bore of the hub of the wheel end assembly.
The sealing system retains lubricant in the wheel end assembly, and particularly at the interface between the axle spindle nut and the outboard bearing, and prevents contaminants from entering the wheel end assembly, thereby increasing the life of the wheel end assembly. The sealing system also retains the relative position of the outboard bearing in the hub during servicing of a brake rotor or components of the wheel end assembly, thereby minimizing potential problems encountered during the disassembly and/or reassembly of the wheel end assembly. Preferably, the sealing system also reduces corrosion at the interface of the hubcap and an outboard face of the hub, and provides an additional barrier that prevents corrosion from entering the wheel end assembly, further increasing the life of the wheel end assembly.
2. Background Art
For many years, the heavy-duty vehicle industry has utilized wheel end assemblies which typically are mounted on each end of one or more non-drive axles. Each wheel end assembly typically includes a hub rotatably mounted on a bearing assembly that in turn is immovably mounted on the outboard end of the axle, commonly known as an axle spindle. As is well known to those skilled in the art, for normal operation of the wheel end assembly to occur, the bearing assembly and surrounding components must be lubricated with a lubricant such as oil, grease, or semi-fluid grease. Therefore, the wheel end assembly must be sealed to prevent leakage of the lubricant, and also to prevent contaminants from entering the assembly, both of which could be detrimental to its performance. More specifically, a hubcap is mounted on an outboard end of the wheel hub, and a main seal or hub seal is rotatably mounted on an inboard end of the hub and the bearing assembly in abutment with the axle spindle, resulting in a closed or sealed wheel end assembly.
While most wheel end assemblies include these general features, the design and arrangement of the hub, bearing assembly, hubcap, main seal, and other components, as well as the axle spindle, vary according to the specific vehicle design and its anticipated uses. For example, hubcaps of the prior art often included a gasket disposed between a flange formed on the inboard end of the hubcap and the outboard surface of the hub. The gasket had been employed to provide a seal between the hubcap and the hub in order to prevent bearing lubricant from leaking out of the wheel end assembly, and to prevent contaminants from entering the assembly. Such hubcaps, while adequate for some applications, typically did not enable precise alignment of the hubcap with the axle spindle, and did not always provide effective seals.
In order to provide precise alignment of the hubcap with the axle spindle and to provide a more effective seal to prevent the bearing lubricant from leaking out of the outboard end of the wheel end assembly, and to prevent water and contaminants from entering the wheel end assembly, an improved prior art hubcap was developed. The improved prior art hubcap is more fully described in U.S. Pat. No. 7,731,300, which is owned by the same assignee as the present invention, Hendrickson USA, L.L.C. The improved prior art hubcap includes a radially-extending flange or shoulder that abuts an outboard face of the hub, and a lip that extends inboardly into a bore of the hub. An O-ring is mounted on the hubcap lip, so that the O-ring is disposed between the hubcap and the hub bore. The O-ring creates a seal between the hub and the hubcap, which provides an outboard seal for the wheel end assembly that retains lubricant in the wheel end assembly and prevents contaminants from entering the wheel end assembly. While such a hubcap works satisfactorily for its intended function, it is desirable to provide an even more effective seal to contain lubricant in the wheel end assembly, and to perform certain additional functions, as will be described in greater detail below.
More particularly, during vehicle operation, the forces that act on the wheel end assembly create a pumping action in the assembly. When semi-fluid grease is employed as the lubricant, this pumping action combines with the shape of the bearings to cause the semi-fluid grease to flow in an outboard direction away from the bearings and the hub, and into the hubcap. Such flow away from the bearings and the hub and into the hubcap creates a greater potential for leakage of lubricant at the hubcap seal to occur. In addition, the viscosity and the tackiness of the semi-fluid grease tends to cause the lubricant to remain in the hubcap when the vehicle is not operating, rather than flowing back to the bearings and the hub. The amount of lubricant that is retained at the bearings is therefore undesirably reduced, which may undesirably impair the operation of the bearings and reduce bearing life.
Moreover, because the hubcap is occasionally removed from the hub by a technician during servicing of the wheel end assembly, semi-fluid grease that remains in the hubcap creates an inconvenience for the technician, as he or she must clean the lubricant out of the hubcap. As a result, it is desirable to provide a sealing system that reduces the flow of lubricant such as semi-fluid grease outboardly away from the bearings and the hub, which reduces or minimizes potential leakage of lubricant, retains the lubricant at the bearings to maintain optimal bearing operation and life, and enables easier servicing of the wheel end assembly.
It is also desirable to provide a structure that properly retains the relative position of the outboard bearing on the hub during disassembly and/or reassembly of the wheel end assembly. Specifically, as mentioned above, the wheel end assembly is closed or sealed to prevent leakage of lubricant, and to reduce the possibility that contaminants may be introduced into the assembly. Over the life of the vehicle, it is necessary to service a brake rotor or other components that may be attached to the wheel end assembly, or components of the wheel end assembly itself. During the servicing of such components, the hub of the wheel end assembly must be removed from the axle spindle in a shop environment. In this disassembly operation, the spindle nut assembly is removed from the axle spindle, and a technician then typically pulls the hub, together with the bearings and main seal, as a unit, off of the axle spindle. During the disassembly process, the engagement of the main seal on the inboard end of the hub typically retains the general position of the inboard bearing. However, in the prior art, once the spindle nut assembly is removed, the outboard bearing lacks positive mechanical engagement With the outboard end of the hub, and may slide out of the outboard end of the hub during the disassembly process.
If the outboard bearing slides out of the hub, it may become damaged, and/or the remainder of the wheel end assembly may be exposed to contaminants, either one of which undesirably can reduce the life of the bearings. In addition, if the outboard bearing slides out of the hub during the disassembly process, or alternatively during reassembly of the wheel end assembly, the outboard end of the hub may undesirably shift or tip radially relative to the axle spindle, which may crimp or kink the main seal on the inboard end of the hub, thereby undesirably causing possible damage to the main seal.
Moreover, during reassembly of the wheel end assembly, it is desirable for the outboard bearing to be retained in a proper position before the spindle nut assembly is installed onto the axle spindle. More particularly, when the outboard bearing is retained in a proper position, the technician is able to focus on installation of the spindle nut assembly onto the axle spindle, rather than on the position of the outboard bearing. Such focus on the installation of the spindle nut assembly is important, as the installation of the spindle nut assembly typically is a precise operation that creates a clamp force on the bearings. If the position of the spindle nut assembly does not create a sufficient clamp force on the bearings and any spacer, there may be excessive end play of the bearings, which in turn creates excessive axial end play of the wheel end assembly relative to the axle spindle, thereby allowing undesirable movement of the main seal that may reduce the life of the main seal and the bearings. If the position of the spindle nut assembly creates a clamp force on the bearings and any spacer that is too high, the bearings may be effectively over-compressed, interfering with their rotation and causing them to possibly wear out prematurely. As a result, optimum positioning of the spindle nut assembly to create an optimum clamp force on the bearings and any spacer is important.
Therefore, movement of the outboard bearing out of the hub during disassembly or reassembly of the wheel end assembly may result in contamination of the wheel end assembly, damage to components, and/or potential improper installation of the spindle nut assembly, all of which result in an undesirable increase in the time and cost associated with the servicing of the wheel end assembly.
In the prior art, retainers have been employed to prevent movement of the outboard bearing out of the hub during disassembly or reassembly of the wheel end assembly. However, these retainers typically have been an integral part of a certain type of spindle nut assembly, which is not readily separable from the hub. More particularly, when a brake rotor or components of the wheel end assembly are to be serviced, certain prior art spindle nut assemblies are designed to be loosened on the axle spindle, and then removed from the axle spindle together with the hub. Some of these spindle nut assemblies include retainers, which possess disadvantages associated with reassembly of the wheel end assembly. For example, these retainers allow the outboard bearing to move somewhat, which creates the possibility that the outboard bearing may be out of position and/or not properly seated when the spindle nut assembly is tightened, thereby binding and thus damaging the bearing.
An improved bearing retainer was developed to retain the relative position of the outboard bearing out of the hub during disassembly or reassembly of the wheel end assembly. The improved bearing retainer includes a structure that improves the accuracy and efficiency of the servicing operation, and is more fully described in U.S. patent application Ser. No. 12/880,757, which is owned by the same assignee as the present invention, Hendrickson USA, L.L.C. The improved bearing retainer includes a circumferentially-extending groove formed in an inner surface of the hub adjacent an outboard surface of the wheel hub, and a retainer ring that seats in the groove. While the improved bearing retainer works satisfactorily for its intended function, it has been found that, under certain conditions during assembly of the retainer ring, the ring may contact and score the surface of the hub bore. Scoring of the surface of the hub bore may impair the integrity of the hub surface, which may in turn reduce the ability of the above-described O-ring to provide an optimum seal, which in turn undesirably increases the potential for bearing lubricant to leak out of the wheel end assembly, and the potential for contaminants to enter the assembly.
Moreover, it is desirable to provide a structure that reduces potential corrosion at the interface of the hubcap and the outboard face of the hub. More particularly, when a heavy-duty vehicle travels over roads and there is moisture on the road surface, road spray may be generated. Road spray is the moisture that is caused to move upward from the road surface by the vehicle tires toward the wheel end assembly, including the hubcap and the hub. Because the hubcap and the hub typically are unprotected from road spray, when the vehicle travels over wet roads, road spray tends to collect on the hubcap and the hub, including at the interface between the hubcap and the hub.
It is known in the art that road spray may include salt or other chemicals that are present on the road surface. For example, salt from salt water is often present on roads near a sea, and rods in areas with abundant ice or snow are often treated with certain chemicals for anti-icing or de-icing, such as sodium chloride, calcium chloride, magnesium chloride, and mixtures thereof. When road spray with salt and/or chemicals collects at the interface between the hubcap and the hub, and the hubcap directly contacts the outboard face of the hub, the moisture and salt and/or other chemicals accumulate at this interface. The accumulation of moisture and salt and/or other chemicals at the interface between the hubcap and the hub may cause galvanic corrosion cells to form. These corrosion cells then tend to propagate, and if there is significant propagation of corrosion cells at the interface between the hubcap and the hub, it may impair the seal between the hubcap and the hub. In the event the seal is impaired, the potential for bearing lubricant to leak out of the wheel end assembly, and the potential for contaminants to enter the assembly, is undesirably increased. In addition, if the corrosion cells continue to propagate, they may spread to components such as the axle spindle nut and/or the bearings, which may reduce the life of such components.
As a result, it is desirable to provide a sealing system that includes a structure which reduces corrosion at the interface of the hubcap and an outboard face of the hub. It is also desirable to provide an additional barrier that prevents contaminants and/or corrosion from entering the wheel end assembly, thereby preserving the life of the assembly.
For these reasons, there is a need in the art to develop an outboard sealing system for a heavy-duty vehicle wheel end assembly that retains lubricant in the wheel end assembly and prevents contaminants from entering the wheel end assembly, retains the relative position of the outboard bearing in the hub during servicing of a brake rotor or components of the wheel end assembly, reduces corrosion at the interface of the hubcap and an outboard face of the hub, and prevents corrosion from entering the wheel end assembly. The outboard sealing system for a heavy-duty vehicle wheel end assembly of the present invention satisfies this need.